JPH11194141A - Current detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and in expensive current detector which has a wide measuring range of current. SOLUTION: This detector is provided with a first gap 14 in which an electromagnetic conversion element 2 is inserted and arranged on the midway of the magnetic circuit of a magnetic core 1 enclosing a conductor W where a current I0 to be detected passes through and allowing a magnetic flux caused by the current to pass through, and a second gap 15 in which a magnetic resistance adjusting body 3 having a permeability different from that of the core 1 is inserted. The cross section of the core 1 is made almost similar to that of the element 2, and the adjustment of magnetic resistance by changing rated current is made only by changing the magnetic resistance of the second gap. Even when the magnetic resistance is changed, the first gap 14 in which the element 2 is inserted is kept unchanged, and the length Lg1 of the gap is kept small and the magnetic flux is kept parallel, and further the cross section of the core is made small, resulting in secure detection by even a compact structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detector for detecting a magnitude of a current flowing through an electric wire connected to an electric device or the like, and more particularly, to adjusting a current value using an inverter or the like. The present invention relates to a device used for monitoring a current value.

[0002]

2. Description of the Related Art Conventionally, there has been disclosed a current detector constituted by a conceptual diagram shown in FIG. 6 (for example, Japanese Patent Application Laid-Open No. 63-85367). That is, a magnetic iron core 10 made of a laminated iron core formed by winding a strip of silicon steel sheet in a ring shape or a dust iron core called a ferrite magnetic iron core using a dust iron core is provided. And a conductor W is passed through the vicinity of the center of the magnetic core 10,
The Hall element 20 as a magnetoelectric conversion element is inserted into the gap 110. When a control current Io is applied from the power supply 201 to the Hall element 20, a through current I
The Hall voltage Vh is detected according to the magnetic flux generated by o, and the Hall voltage Vh is amplified by the operational amplifier 202 connected to the Hall element 20.

In general, when a through current Io is passed through a conductor W passing through the center of a ring-shaped magnetic circuit having a gap 110 having a length Lg, a magnetic flux B passing through a magnetic core 10 is formed.
Is given by the following equation, where μs is the magnetic permeability of the magnetic material of the magnetic circuit, Lc is the magnetic path length of the magnetic circuit, and μo is the magnetic permeability of the vacuum. B = (μs · μo · Io) / (μs · Lg + Lc) Normally, μs · Lg >> Lc, so the above equation is as follows. B = (μo · Io) / Lg From this equation, it can be seen that the magnetic flux B is almost proportional to the through current Io, and this relationship is maintained until the magnetic saturation of the magnetic path material. Gap 1 of magnetic core 10 forming this magnetic circuit
When the Hall element 20 is inserted into the element 10 and a control current Io is supplied to the Hall element 20, a Hall voltage Vh proportional to the through current Io can be detected via the operational amplifier 202.

However, if the magnetic flux of the magnetic core 10 is excessively increased, magnetic saturation may occur or the Hall element 20 may have a magnetic saturation of 0.0.
When a magnetic flux larger than about 5 Tesla is applied, the magnetic flux and the Hall voltage Vh become non-linear, and the linearity between the through current Io and the Hall voltage Vh is lost. Therefore, in general, in the current detector, the facing surface of the gap 11 of the magnetic iron core 10 is machined according to the rated current value flowing through the conductor W to change the length Lg of the gap 110 so as to cope with various rated currents. Let me. In the case where the magnetic core 10 is formed by winding a strip of magnetic material, a directional magnetic steel strip having a high magnetic permeability in the longitudinal direction is generally used. In order to remove distortion caused by bending, annealing is performed after lamination, and then the gap 110 is cut and polished to manufacture.

Incidentally, in the conventional current detector shown in FIG. 6, even if an attempt is made to fix the Hall element 20 to the center of the gap 110, a slight displacement of the holding position occurs. For this reason, the magnetic core 1 of these current detectors is generally used.
0 is configured so that the magnetic flux in the gap 110 is parallel, so that even if the position of the Hall element 20 is slightly shifted, the measured magnetic flux is not affected. Gap 11 to make it parallel
The value of the square root of the cross-sectional area of 0 (the length of one side when the cross section of the gap 110 is a square, and the diameter when the cross section is a circle) is set to be about three times or more the gap length Lg. . That is, the sectional area A of the magnetic core 10 and the gap 11
The relationship of the length Lg of 0 is such that A / Lg ² ≧ 3 (1)

[0006]

However, when the current value Io of the through current to be detected is large, the gap length Lg is increased to increase the magnetic resistance and the gap 110 to prevent the magnetic iron core 10 from being saturated. It is necessary to suppress the passing magnetic flux. However, when the gap length Lg is increased, it is necessary to increase the cross-sectional area of the magnetic core 10 according to the above equation (1) in order to make the magnetic flux in the gap 110 parallel. However, there was a problem that it became expensive. In addition, when PWM control or chopper control is performed on the through current to be detected, a harmonic current component is superimposed, and unlike the case of detecting a low-frequency current about the commercial frequency, a silicon steel plate forming the magnetic iron core 10 Eddy current loss increases. Therefore, the magnetic core 1
However, there is a disadvantage that the heat generation amount of 0 becomes large, the limitation of the operating temperature range is narrowed, and the current detection characteristic is deteriorated due to a temperature change. In addition, the manufacturing process of the magnetic core 10 requires an annealing process for removing distortion and a cutting and polishing process for the gap 110.
And the price of the current detector becomes expensive. SUMMARY OF THE INVENTION It is an object of the present invention to provide a small and inexpensive current detector that can adjust the magnetic resistance of a magnetic core without increasing the cross-sectional area of the magnetic core, and has a wide current measurement range.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a magnetic core surrounding a conductor through which a current to be detected flows and passing a magnetic flux generated by the conductor, and a magnetic circuit of the magnetic core. The gap provided in the middle of
In a current detector including a magnetoelectric conversion element installed in the gap, a cross-sectional area of the magnetic iron core is set to be slightly larger than a cross-sectional area of the magnetoelectric conversion element. A first gap into which a magnetoelectric conversion element is inserted and at least one second gap into which a magnetoresistance adjuster having a magnetic permeability different from that of the magnetic iron core is inserted are provided.

[0008]

According to an aspect of the present invention, there is provided a magnetic core in which legs of two U-shaped iron core members are opposed to each other, and a first gap and a second gap are formed between the opposed legs. A conductor through which a current to be detected flows is inserted into a space surrounded by a circle, the cross-sectional area of the magnetic core is set to be slightly larger than the cross-sectional area of the magnetoelectric conversion element, and the magnetoelectric conversion element is inserted into the first gap. The gap length is slightly larger than the thickness of the magneto-electric conversion element, and a magnetic resistance adjuster having a magnetic permeability different from that of the magnetic core is inserted into the second gap to adjust the magnetic resistance. Adjusted according to the body. In addition, the said magnetic iron core laminates a magnetic plate,
Alternatively, a magnetic material powder that is solidified integrally with a resin can be used, and is divided into a plurality of iron core members to form a square or round shape. The magnetoresistive adjuster is a laminated body of a non-magnetic metal sheet, a laminated body of a non-magnetic metal sheet and a magnetic metal sheet, a magnetic substance powder solidified integrally with a resin, or a porous body. Can be used. Further, the magnetoelectric conversion element is constituted by a Hall effect element. Note that a gap stopper for protecting the magneto-electric conversion element can be provided in the first gap. Further, a box for accommodating the magnetic core can be provided, and an elastic core holding plate for holding the magnetic core and the magnetic resistance adjuster in close contact with each other can be provided in the box.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a current detector according to a first embodiment of the present invention. Reference numeral 1 denotes a magnetic iron core, which is composed of two U-shaped iron core members 12 and 13, and includes a leg 12 a and a leg 13.
A first gap 14 having a length Lg1 is provided between the opposed end faces of the leg 12a and the length Lg1 between the opposed end faces of the leg 12b and the leg 13b.
The second gap 15 of g2 is formed. The iron core members 12 and 13 are formed by laminating a U-shaped punched plate 11 punched out from a thin steel plate of a directional magnetic strip by pressing a joint between legs in a direction of high magnetic permeability. ing. Reference numeral 16 denotes a space surrounded by the iron core members 12 and 13 in a rectangular shape, through which the conducting wire W passes. In addition, embossed portions 17 are provided at several places on the surface of the punched plate 11 of the iron core members 12 and 13 at the same time as punching with a press, and arc-shaped portions are formed inside the corners to prevent magnetic flux leakage. ) 18 are provided. The core member 1
The width of the magnetic path of the punched plate 11 that forms
Of the magneto-electric conversion element 2 to be inserted into the gap 14 (2.3 mm) in the width direction (for example, 4 mm).
mm), the plate thickness is selected to be about 0.1 mm because the eddy current loss increases as the thickness increases, and the handling during pressing becomes difficult when the thickness decreases. A required number of sheets, for example, about 50 sheets are stacked so as to be slightly larger (for example, 5 mm) from the dimension (for example, 4 mm). Thus, iron core members 12 and 13 are formed.

Reference numeral 2 denotes a magneto-electric conversion element comprising a Hall effect element, which is inserted and disposed in the first gap 14 and, when a control current Ic is supplied from the power supply 21 to the magneto-electric conversion element 2 as shown in FIG. The magnetic flux φ generated by the through current Io flowing through the conducting wire W acts on the magnetoelectric conversion element 2, and the Hall voltage Vh proportional to the through current Io can be detected via the operational amplifier 22. Numeral 3 denotes a non-magnetic material such as copper, which is inserted into the second gap 15 and has a magnetic permeability different from that of the magnetic core 1, and regulates the length of the second gap 15.
The magnetic resistance of the magnetic core 1 is adjusted. Numeral 4 denotes a box housing the two core members 12 and 13,
Are arranged such that a rectangular space 16 is formed. Reference numeral 41 denotes a nonmagnetic gap stopper which is provided in contact with the opposing surface of the first gap 14 and holds the gap. The gap stopper 41 regulates the length Lg1 of the first gap 14, and the core members 12 and 13 are used for the electromagnetic conversion. The element 2 is compressed to protect it from being damaged. Reference numerals 42 and 43 denote elastic core holding plates fixed to the box body 4. Elastic plates are provided at a plurality of positions outside the iron core members 12 and 13 to hold the magnetic iron core 1.

When a through current Io is passed through a conductor W passing substantially through the center of a magnetic core 1 having a first gap 14 having a length Lg1 and a second gap 15 having a length Lg2, the magnetic material of the magnetic core 1 is formed. Is μs, the magnetic path length of the magnetic core 10 is Lc, the magnetic permeability of vacuum is μo, and μs Lg >> Lc, the magnetic flux B passing through the magnetic core 10 is expressed by the following equation. B ≒ (μo × Io) / (Lg1 + Lg2) The magnetic flux B is almost proportional to the through current Io, and the first gap 1
It can be seen that the length Lg1 is inversely proportional to the sum of the length Lg1 and the length Lg2 of the second gap 15. As described above, the magnetic core 1 having the first gap 14 and the second gap 15
Can change the magnetic resistance by changing the length Lg2 of the magnetoresistive adjuster 3 inserted in the second gap 15, so that the rated current of the conductor W changes and the magnetic core 1 changes in accordance with the magnitude of the through current Io. When it is necessary to change the magnetic resistance of the first gap 14, there is no need to change the length Lg1 of the first gap 14 from a small value enough to insert the magnetoelectric conversion element 2, and the sectional area of the first gap 14 is changed to the length Lg1. , And the magnetic flux can be kept parallel. In order to increase the magnetic resistance, the length Lg of the second gap 15 is
By making 2 larger regardless of the cross-sectional area of the magnetic core 1, even if the magnetic flux in the second gap 15 does not become parallel, it does not affect the magnetoelectric conversion element 2 and does not pose a problem.

Therefore, the first gap 14 can always keep the magnetic flux parallel by reducing the gap length, and the first gap 14 can be changed only by changing the thickness of the magnetoresistive adjuster 3 by the second gap 15. 14 and the magneto-electric conversion element 2, the magnetic resistance of the magnetic circuit can be adjusted in accordance with the rated value of the through current Io to be measured, and the components can be standardized. Will be possible. Further, even the magnetic core 1 having a small cross-sectional area can be used for a current detector having a large through current, and the cost can be reduced. Further, even when a harmonic current component is superimposed on a through current Io to be detected, such as in PWM or chopper control, the volume of the magnetic core 1 can be reduced, and thus the heat generation of the magnetic core 1 due to eddy current loss. Can be held down. The box 4 also includes iron core holding plates 42 and 43.
To hold the magnetic core 1, and the core member 12 with a large area,
Since the box 13 is in contact with the box 4, the heat generated by the eddy current can be effectively radiated to the box, and the temperature rise of the magnetic circuit can be suppressed. Further, the iron core members 12, 1
No. 3 processes a flat directional magnetic strip with a press die, so that bending stress is not applied and an annealing process is not required. Therefore, the magnetic iron core 10 can be manufactured at low cost with a small number of work steps.
Since the number of steps is small and the steps are simple, automation can be easily performed, and manufacturing equipment costs can be reduced.

FIG. 3 is a front view showing a current detector according to a second embodiment of the present invention. In the second embodiment, the magnetic iron core 1 is formed in a donut shape using the semi-lunar iron core members 12 and 13, and a first gap 14 and a second gap 15 are provided in the middle of the iron core. The conversion element 2 and the magnetoresistance adjuster 3 are inserted. For this reason, a magnetic circuit having a smooth curve is formed along the flow of the magnetic flux formed by the conductor W, so that magnetic flux leakage at corners is minimized as compared with a magnetic circuit in which a U-shaped iron core member is opposed. Can be. The shape of the box 4 having the iron core holding plate 42 can be circular around the magnetic iron core 1. However, if the fixing becomes unstable when installing the current detector, the box 4 The body 4 can be, for example, hexagonal or octagonal.

FIG. 4 is a front view showing a current detector according to a third embodiment of the present invention. In this embodiment, the magnetic core 1 is divided into four L-shaped core members 19 having the same shape, and both end surfaces of each core member 19 are opposed to each other via a gap, so that the square-shaped magnetic core 1 is formed. Are formed, and four gaps are provided. One of the four gaps is
The first gap 14 is formed, the magneto-electric conversion element 2 is inserted, and the through current Io is measured. The other three gaps are provided with a magneto-resistance adjuster for adjusting the magnetic resistance of the magnetic iron core 1. 3 to insert the second gaps 15a, 15b,
15c. The first gap 14 and the second gap 15a on the opposite side have a gap length of Lg1, and the second gaps 15b, 15 on both sides.
The gap length Lg2 of c is adjusted according to the magnetic resistance. Therefore, in this embodiment, since the shape of the iron core member 19 is the same, the press die can be made inexpensive, and the yield when pressing from a hoop material of a thin steel plate is improved by the shape of the punched plate, and the magnetic resistance is reduced. The adjustment can be performed by simply changing the position of the iron core member without cutting the gap. Reference numeral 17 denotes an embossed portion for stacking and connecting the punched plates, and reference numeral 42 denotes an iron core holding plate attached to the box 4.

FIG. 5 is a front view showing a current detector according to a fourth embodiment of the present invention. The magnetic core 1 is formed by the three divided core members 19A, 19B, 19C,
L-shaped core members 19A and 19B facing each other via the first gap 14, and core members 19A and 19B.
B-shaped iron core member 19 forming a magnetic circuit opposite to B
C, and core members 19A and 19B and a core member 19C.
And second gaps 15d and 15e are formed between them, and the magnetoresistive adjuster 3 is inserted into each of them. Therefore, similarly to the fourth embodiment shown in FIG. 4, when adjusting the magnetic resistance of the magnetic iron core 1, only the length of the magnetic resistance adjuster 3 needs to be changed, and the magnetic resistance adjusters 3A and 3B are not used. If equal, the distance between the iron core members 19A, 19B and the iron core member 19C may be changed, so that it is not necessary to cut the iron core member by machining in order to adjust the magnetic resistance. Since the number is small, costs and man-hours can be significantly reduced.

In the above embodiment, the example in which the magnetoresistive adjuster 3 is made of a nonmagnetic metal such as copper has been described. However, only the nonmagnetic metal plate or a laminate of nonmagnetic metal plates including the magnetic metal plate is described. Alternatively, the magnetic resistance adjuster 3 having a different magnetic permeability from that of the iron core member can be formed of a plastic material obtained by mixing a powder of a magnetic substance such as iron powder into a resin or the like and solidifying the magnetic material. By forming a large number of holes in a block of a magnetic material or by forming a porous body using a sintered body of a magnetic material, the magnetic resistance adjuster 3 having a magnetic permeability different from that of the iron core member may be formed. In order to adjust the magnetic resistance, the second
However, for example, by arbitrarily determining the ratio of the magnetic metal plate and the non-magnetic metal plate, and the ratio of the powder of the magnetic material, the magnetic core can be changed without changing the size of the core member. The magnetic resistance of the magnetic open circuit may be changed by arbitrarily setting the magnetic resistance of the first magnetic field.

[0017]

As described above, according to the present invention, the first gap and the second gap are provided in the middle of the magnetic circuit of the magnetic iron core, and the magnetoelectric conversion element is inserted into the first gap.
Since the magnetic resistance adjuster is inserted into the second gap to adjust the magnetic resistance of the magnetic iron core, even if the value of the through current to be measured is large and a large magnetic resistance is required, the first magnetic resistance adjuster is used. Even if the gap is kept small according to the thickness of the magnetoelectric transducer and the cross-sectional area of the magnetic core is reduced,
Since it can be maintained at least three times the square of the length of the first gap, the size of the magnetic core becomes small, and the parallelism of the magnetic flux in the first gap can always be ensured to maintain the performance of the magnetoelectric conversion element. , The outer shape of the current detector can be reduced,
An inexpensive current detector can be provided. Furthermore, since the size of the magnetic core is small, even when a harmonic current component is superimposed on a through current to be detected, such as in PWM control or chopper control, the amount of heat generated by the magnetic core due to eddy current loss is small. Thus, a high-performance current detector can be provided.

Further, by providing a plurality of second gaps, the gap length can be adjusted by adjusting the mounting positions of the core members without cutting the magnetic core.
The shape of the core members constituting the magnetic core can be made the same, parts can be shared, and the magnetic core can be manufactured at low cost.
Any effect that a current detector can be provided inexpensively with small-scale equipment can be obtained. Note that the resistance value can be increased by using a metal sheet laminate containing a non-magnetic metal as the magnetoresistive adjuster, or by solidifying a magnetic powder into a solid with resin, or by using a porous magnetic material. Can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a magnetic circuit according to a first embodiment of the present invention.

FIG. 3 is a front view showing a second embodiment of the present invention.

FIG. 4 is a front view showing a third embodiment of the present invention.

FIG. 5 is a front view showing a fourth embodiment 4 of the present invention.

FIG. 6 is a configuration diagram showing a conventional example.

[Explanation of symbols]

1: magnetic core 2: magneto-electric conversion element 3: magnetic resistance adjuster, 11: punched plate 12, 13: iron core member 12a, 12b, 13a, 13b: leg 14: first gap 15 15a, 15b, 15c, 15d , 15e: second
16: Space portion 17: Emboss portion 18: Arc portion 19, 19A, 19B, 19C: Iron core member 21: Power supply 22: Operational amplifier 4: Box 41: Gap stopper 42, 43: Iron core holding plate

Claims (10)

[Claims] A magnetic core that surrounds a conductor through which a current to be detected flows and allows a magnetic flux generated by the conductor to pass therethrough; and a gap provided in the magnetic circuit of the magnetic core.
In a current detector including a magneto-electric conversion element installed in the gap, a cross-sectional area of the magnetic iron core is set to approximately the same size as a cross-sectional area of the magneto-electric conversion element, and the magneto-electric conversion element is inserted. A first gap having a reduced gap length and a second gap having a magnetic resistance adjuster having a magnetic permeability different from that of the magnetic core inserted therein and adjusted to a gap length corresponding to the magnetic resistance adjuster were provided. A current detector, characterized in that: 2. The magnetic core according to claim 1, wherein the magnetic core includes a first gap into which a magnetoelectric conversion element is inserted and a plurality of second gaps into which a magnetoresistance adjuster is inserted. Current detector. 3. The current detector according to claim 1, wherein said magnetoelectric conversion element is constituted by a Hall effect element. 4. The current detector according to claim 1, wherein the magnetoresistance adjuster is made of a metal body made of a nonmagnetic metal. 5. The current detector according to claim 1, wherein the magnetoresistance adjuster is formed of a laminate including a nonmagnetic metal plate. 6. The current detector according to claim 1, wherein the magnetic resistance adjuster is formed by solidifying a magnetic substance powder with a resin. 7. The current detector according to claim 1, wherein the magnetoresistance adjuster is made of a porous magnetic material. 8. The magnetic core includes two U-shaped core members, the legs of the core members opposing each other, and a first gap and a second gap are formed between the opposing legs. The current detector according to any one of claims 1 to 7, wherein: 9. The magnetic core has one end face facing the first core.
A first iron core member and a second iron core member opposed to each other via a gap, and a third iron core member opposed to the other end surfaces of the first iron core member and the second iron core member via a second gap.
8. The current detector according to claim 1, wherein a magnetic circuit is formed by the iron core member. 10. A core body for accommodating the magnetic iron core, and an iron core holding plate made of an elastic body for holding the magnetic iron core and the magnetic resistance adjuster in close contact with each other is provided on the box body. The current detector according to any one of claims 1 to 9, wherein: